An etching apparatus that performs an etching processing on a workpiece (e.g., a semiconductor wafer) using plasma has been known in the related art. Such an etching processing apparatus includes a placement table within a processing container that is designed to be capable of forming a vacuum space therein. The placement table is configured to place a workpiece therein and also functions as an electrode of the etching apparatus. In the etching processing apparatus, an etching processing using plasma is performed on a workpiece placed on the placement table by applying, for example, a predetermined radio-frequency power to the placement table. In addition, in the etching apparatus, radio-frequency power may be applied to the placement table for bias purpose when the etching processing is performed using plasma. By applying radio-frequency power to the placement table for bias purpose, the ions in the plasma are drawn into the workpiece, and holes and grooves are efficiently formed in the workpiece.
In recent years, an aspect ratio required for holes or grooves formed in a workpiece by an etching processing is increasing. In an etching processing of holes or grooves having a high aspect ratio, as the etching processing progresses, since the rectilinearity of the ions drawn into the workpiece decreases, etching characteristics deteriorate. It is known that the rectilinearity of the ions drawn into the workpiece becomes higher as the frequency of the radio-frequency power for bias applied to the placement table becomes lower.
Thus, there has been known a technique in which a plurality of radio-frequency power supplies for generating a plurality of radio-frequency powers for bias having different frequencies are mounted in an etching apparatus and the frequency of the radio-frequency power for bias is changed by selectively switching connection between the plurality of radio-frequency power supplies and the placement table during the etching processing. See, for example, Japanese Patent Laid-open Publication No. 2008-053516.